Photographic apparatus with built-in exposure control assembly

ABSTRACT

A photographic camera wherein the pointer of a moving-coil measuring instrument is scanned by a device which adjusts the diaphragm and/or the shutter when the exposure control assembly of the camera is set for automatic determination of exposure values. When the exposure control assembly is set for the making of exposures with a relatively long exposure time, the instrument is connected with the output of a circuit whose input is then connected with a timer including a photosensitive resistor and a capacitor which is charged by way of the resistor to cause the circuit to move the pointer to an end position when the capacitor is charged to a predetermined value. The user of the camera opens the shutter to thereby complete the circuit and observes the pointer to close the shutter when the pointer is caused to assume its end position. The photosensitive resistor is in circuit with the moving coil of the instrument when the exposure control assembly is set for automatic determination of exposure values.

United States Patent Wagner et al. 45 J 25, 1972 [54] PHOTOGRAPHICAPPARATUS WITH 3,299,789 1/1967 Chandler et al ..95/64 D BUILT-INEXPOSURE CONTROL 3,455,219 7/1969 Burgarella ....95/l0 CD ASSEMBLYPrimary Examiner-Joseph F. Peters, Jr. [72] Inventors: Karl Wagner,Ottobrunn; Josef Ganser, Attorney-Michael S. Striker Munich, both ofGermany [73] Assignee: Agfa-Gevaert Aktiengesellschaft, Lever- [57]ABSTRACT kusen, Germany A photographic camera wherein the pointer of amoving-coil measuring instrument is scanned by a device which adjuststhe [22] 1971 diaphragm and/or the shutter when the exposure control as-[21] A N 109,811 sembly of the camera is set for automatic determinationof exposure values. When the exposure control assembly is set for themaking of exposures with a relatively long exposure time, [30] Fol-mgApphcano Pnomy Data the instrument is connected with the output of acircuit whose Jam 30 97 Germany 20 Q4 2595 input is then connected witha timer including a photosensitive resistor and a capacitor which ischarged by way of the resistor 52 U.S.Cl. ..9s/10 CT, 95/53 EB to causethe eireuit t9 meve the Pointer to an end Position 511 int. Cl. ....G03b7 04, G03b 7 12, G03b 9/58 when the eapeeiter is charged to apredetermined value- The 58 Field of Search ..95/1o c, 10 CE, 10 c1), 10CT, of the camera Opens the shutter to thereby Complete t 95 53 13, 53EA, 5 EB, 64 R, 64 D circuit and observes the pointer to close theshutter when the pointer is caused to assume its end position. Thephotosensi- 5 Reerences Cited tive resistor is in circuit with themoving coil of the instrument when the exposure control assembly is setfor automatic deter- UNITED STATES PATENTS mination of exposure values.3,269,287 8/1966 0st ..95/l0 CT 15 Claims, 2 Drawing Figures PATENTEDJANZS 2972 SHEET 1 (IF 2 INVENTOR KARL WAGNER JOSEF GANSER Z/w///4-,4.,/

PATENIEDEJANZS I972 SHEEI 2 0f 2 INVENTOR KARL WAGNER JOSEF GANSERPIIO'IOGRAPIIIC APPARATUS WITH: BUILT-IN EXPOSURE CONTROL ASSEMBLYBACKGROUND OF THE INVENTION relates to improvements in photographicapparatus of the type wherein the moving-coil measuring instrument formspart of an exposure control assembly which is capable of automaticallydetermining one or two exposure values (exposuretime and aperture size)as a of scene brightness.

SUMMARY OF THE INVENTION An object of the invention is to provide aphotographic apparatus having a built-in exposure control assemblyutilizing an electrical moving-coil measuring instrument forautomaticdetermination of one or more exposure values as a function of scenebrightness with novel means for indicating to the user the optimumlength of relatively long exposuretimeswhich are needed when the scenebrightness is low, especially when the scene brightness isunsatisfactory for the making of exposures with the camera held by hand.

Another object of the invention is to construct and assemble theautomatic exposure control assembly of a photographic apparatus in sucha way that its component parts can be used to indicate relatively longexposure times, namely, exposure times which are longer then thosedetermined bytheexposure control assembly when the assembly is set forautomatic determination of exposure time and/or aperture size independency on the intensity of scene light.

The invention is embodied in an exposure control assembly which is builtinto a photographic apparatus and comprises an electrical moving-coilmeasuring instrument having a pointer or indicator movable to and from apredetermined position which represents the optimum length of arelatively long exposure time at a low scene brightness, timer meansincluding photosensitive receiver means which isexposed to scene lightandcapacitor means which can be charged by way of the receiver means ata rate which is a function of scene brightness, a moving circuit havinga high-resistance input which is connectable with the timer means and anoutput which is connectable with the measuring instrument to efiect amovement of .the indicator to the predetermined position in response tocharging of the capacitor means to a predetermined value, switch meanswhich connects the receiver means with the measuring instrument when theexposure control as- BRIEF DESCRIPTIONOF THEDRAWING FIG. 1 .isaschematicfragmentary sectional view of a still camera having an exposurecontrolassembly which embodies one form of the invention; and

FIG. 2 is a similar view ot' a camera having a modified exposure controlassembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FlG.- l.'illustrates a. portionof a still camera having a housing or-body'l whichcontains an electricalmoving-coilmeasuring instrumentZ having an indicator orpointer 3 whichismova- -ble between a pluralityofpositions including apredeterminedend-position indicated-by markers'4..A scanning'merfnber 5 has aninclined scanning face'Sa and is movable up and down, as viewediinFlG.l,-into and out of engagementwith-the needle 3. The scanning member! isbiased towardthe needle 3 by .a' relatively weak'helical spring 6 andhasa 'projection -5b which normally .abuts against alcollar 8a vprovided'ona .depressible release element8 which is'biased upwardly to theillustrated starting position by a relatively strong helical returnspring 7. When nofinger'pressure is exerted against-the .ex-

.posed upper end portion of the release element 8, the spring 7overcomes the action of the spring 6 and maintains the scanning memberSin-the upper end position which is shown in the drawing. 5

A blocking pawl'9 which is pivotablymounted in the hous-. ing 1 has ashorter arm moveable intothe path of movement of an extension Scofthescanning member 5 and a longer arm which is coupled to a reciprocablemotion transmitting member 10 by a helical spring 9a. The lower endportion of the member '10 is articulately connected to a manuallyrotatable adjusting ring 11 by a -pin-and-slot connection, and-thehousing 1 has guide pins'la which confine the member 10 to reciprocatorymovement. The adjusting-ring ll isprovided with an index 12 which is.movable intoregistry with symbols provided on a fixedly mounted scale13. .These symbolsinelude a-character A which indicatesthat the exposurecontrol assembly of the camera is set for automatic operation, a

' mounted inthe housing I to receive scent light which passes sembly isset for automatic determination of exposure time and/or aperture sizeand which is actuatable toconnect the output of the moving circuit withthe measuring instrument, to connect the receiver means with thecapacitor meansand to connect the timer means with the input of themoving circuit, and adjusting means movable between a first position tothereby set the exposure control assembly for automatic determination ofone or both exposure values and a second position to thereby actuate theswitch means. The user of the apparatus opens the shutter to therebyconnect the parts of the circuitry with an energy source and maintainsthe shutter in open position until the indicator reaches itspredetermined position. Such manual closing of the shutter takes placewhen the exposure time is relatively long. The shutter is closedautomatically when the exposure control assembly is set for automaticoperation.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved photographicapparatus itself, however, both as to itsconstruction and its mode of operation, together with additionalfeatures and advantages thereof, will be best through an auxiliarylight-obstructing diaphragm 15. The auxiliary diaphragm '15 isadjustable in response to adjustment of the main diaphragm behind thepicture-taking lens L. A switch .16 must be closed in order to connectone terminal of the photoelectric resistor 14 with the negative pole ofan energy source 17. The other terminal of the resistor l4 isconnectable with one terminal of the coil in the measuring instrument 2by way of a first two-way switch'l9 and a secopd twoway switch 21. Theswitch 19 -has .a median contact 18 which can be moved intoengagementwith a fixed contact 18a or 18b, and the switch 21 has a median contact20 which is movable into engagementwith a fixed contact 20a or 20b.'-Theother terminal of the coil in the measuring instrument 2 is connectablewith the positive pole of the energy source "by way of a third two-wayswitch 23 having a median contact 22 which can engage a fixed contact220 or 22b.

When the median contact 18 of the two-way switch 19 engages the fixedcontact l8b, the oneterrninal of the photoelectric resistor 14 isconnected with the base of a first transistor 24. The resistor 14 isthen in series with a capacitor 25 and forms therewith a timer whichdetermines the rate of speed of movement of the pointer 3 into registrywith the markers 4. The two-way switch 18 is adjacent to an auxiliaryswitch 26 which is closed when the contact 18 engages the contact 18aand opens in response to movement of the contact 18 into engagement withthe contact 18b. The auxiliary switch 26. is connected in parallel withthe capacitor 25. A switch 27 can be closed to short circuit thecapacitor 25;the switch 27 opens in automatic response to movement ofthe shutter (not shown) toward its open position.

The collector circuit of the transistor 24 includes a resistor 28 andthe emitter of the transistor 24 is connected with the base of a secondtransistor 29. The collector circuit of the transistor 29 includes aresistor 30 and the emitter of the transistor 29 is connected with thebase of a third transistor 31. The emitter circuit of the transistor 31includes a variable resistor 32 and the collector of the transistor 31is connected with the coil of the measuring instrument 2 when the mediancontact 20 of the switch 21 engages the contact 20b. The lefthandterminal of the coil in the measuring instrument 2 is connected with thenegative pole of the energy source 17 in response to engagement of themedian contact 22 with the fixed contact 22b when the switch 16 isclosed.

The adjusting ring 11 is provided with two cams 33, 34 the first ofwhich serves to move the median contact 22 of the switch 23 intoengagement with the fixed contact 22b when the ring 1 l is rotated in acounterclockwise direction from the angular position shown in FIG. 1.The cam 34 can move the median contact 18 of the switch 19 intoengagement with the fixed contact 18b to thereby open the auxiliaryswitch 26 when the adjusting ring 11 is rotated in a counterclockwisedirection beyond the angular position shown in FIG. 1. A trip 35 whichbears against an extension of the median contact 22 and is secured tothe median contact 20 causes the latter to move into engagement with thecontact 20b when the contact 22 engages the contact 22b. A similar trip36 is provided on the lower contact of the auxiliary switch 26 to movethis lower contact away from the upper contact when the cam 34 moves thecontact 18 into engagement with the contact 18b.

It is to be noted that the cams 33, 34 can be (and normally are)replaced with a single cam having a face which is configurated in such away that it can engage the contacts 18 and 22 in certain angularpositions of the adjusting ring 11.

The pointer 3 of the light meter 2 is observable from without thehousing 1, at least at such times when the pointer registers with themarkers 4.

The operation:

it is assumed that the index 12 of the adjusting ring 11 registers withthe symbol A on the scale 13. The extension 50 of the scanning member 5is not engaged by the shorter arm of the blocking pawl 9. If the user ofthe camera wishes to make an exposure, the release element 8 isdepressed against the opposition of the return spring 7 whereby thecollar 8a moves downwardly and the spring 6 is free to contract so as tomove the inclined face 5a of the scanning member 5 into engagement withthe pointer 3 whereby the member 5 is arrested in a position which is afunction of the angular position of the pointer, i.e., a function of theprevailing scene brightness. As shown in FIG. 1, the coil of themeasuring instrument 2 is connected in series with the photosensitivereceiver 14 when the index 12 of the adjusting ring 11 registers withthe symbol A of the scale 13. The scanning member 5 is operativelyconnected with and serves to adjust the main diaphragm 115 (and hencethe auxiliary light-obstructing diaphragm 15) and/or the shutter as afunction of scene brightness, namely, as a function of the angularposition of the pointer 3. The transistors 24, 29 and 31 block becausethe base of the transistor 24 is connected with the positive pole of theenergy source 17 by way of the auxiliary switch 26. The release element8 opens the shutter in response to further depression beyond thatposition in which the inclined face 5a of the scanning member 5 ispermitted to engage the pointer 3, i.e., subsequent to appropriateautomatic adjustment of the shutter and/or diaphragm 115 as a functionof scene brightness. The extension 50 of the scanning member 5 is freeto bypass the shorter arm of the blocking pawl when the index 12registers with the symbol A on the scale 13.

If the user wishes to make an exposure with a relatively long exposuretime, the adjusting ring 11 is rotated by hand so as to place the index12 into registry with the symbol B of the scale 13. Themotion-transmitting member is then moved downwardly, as viewed in FIG.1, and the spring 911 pivots the blocking pawl 9 so that the left-handarm of the pawl extends into the path of movement of the extension 50 onthe scanning member 5. The release element 8 is thereupon depressedagainst the opposition of the spring 7 whereby the spring 6 tends tomove the scanning member 5 downwardly but such movement of the member 5is prevented by the left-hand arm of the blocking pawl 9 (i.e., by theadjusting ring 11 through the intermediary of the member 10, spring 9aand pawl 9. Thus, the inclined face 5a of the scanning member 5 cannotreach the pointer 3 of the measuring instrument 2. Furthermore, when theadjusting ring 11 is rotated to move the index 12 into registry with thesymbol B, the cams 33 and 34 cause the auxiliary switch 26 to open, themedian contact 18 of the switch 19 to engage the contact 18b, the mediancontact 22 of the switch 23 to engage the contact 221;, and the mediancontact 20 of the switch 21 to engage the contact 2012. Thus, thephotosensitive resistor 14 is connected in series with the capacitor 25and the coil of the measuring instrument 2 is connected in the outputcircuit of the transistor 31. The release element 18 also closes theswitch 16 and thereupon opens the shutter. The switch 27 is caused toopen following opening of the shutter (in a manner not shown in thedrawing). Opening of the switch 27 enables the capacitor 25 to becomecharged by way of the photosensitive resistor 14. During such charging,the potential at the base of the transistor 24 rises so that thetransistor 24 begins to conduct whereby the rise of its conductivitydepends on the rate at which the capacitor 25 is charged by way of theresistor 14. The current flowing in the collector-emitter circuit of thetransistor 24 is amplified by the transistors 29 and 31 so that thestrength of the current flowing through the coil of the measuringinstrument 2 begins to rise. The angular position of the pointer 3changes at a speed which depends on the prevailing scene brightness(which is I detected by the resistor 14 and determines the rate at whichthe capacitor 25 is charged). The pointer 3 travels toward the positionof registry with the markers 4. The user of the camera terminates thepressure against the head of the release element 8 when the pointer 3registers with the markers 4 whereby the shutter of the camera is causedto close in a manner not forming part of the present invention. Thecircuit of the energy source 17 opens automatically in response toclosing of the shutter.

In accordance with a modification, the switch 16 can remain in closedposition after the release element 8 is permitted to reassume itsstarting position and the switch 16 opens only in response to reneweddepression of the element The transistors 24, 29, 31 are connected incascade and together constitute a moving circuit (for the pointer 3)having a high-resistance input connected with the timer including theresistor 14 and capacitor 25 and an output connected with the coil ofthe instrument 2 when the adjusting ring 11 actuates the switch means19, 21, 23, 26 in response to movement of its index 12 into registrywith the symbol B on the scale 13. The switches 19, 21 are connected inseries when the index 12 registers with the symbol A to thereby connectthe resistor 14 in series with the coil of the measuring instrument 2.When the index 12 registers with the symbol B, the switch 19 connectsthe resistor 14 with the capacitor 25 and the switch 21 connects theoutput of the moving circuit 24, 29, 31 with the measuring instrument 2.The auxiliary switch 26 is then open and the switch 23 connects themeasuring instrument 2 with one pole of the energy source 17 (by way ofthe switch 16). When the index 12 registers with the symbol A, theswitch 23 connects the coil of the measuring instrument 2 with the otherpole of the energy source 17 and the auxiliary switch 26 is closed.

When the index 12 registers with the symbol B, the low internalresistance of the measuring instrument 2 is transformed into a higherohmic resistance by the moving circuit 24, 29, 31 so as not to influencethe charging of the capacitor 15 in dependency on scene brightness.While the capacitor 25 is being charged, the rising voltage influencesthe coil of the measuring instrument 2 to move the pointer 3 towardregistry with the markers 4.

The reference character 50 denotes a viewfinder which is indicated byphantom lines. The viewfinder 50 has a window 51 which is located infront of the pointer 3 when the latter registers with the markers 4.

The purpose of the blocking pawl 9 is to prevent the scanning member 5from interfering with movement of the pointer 3 to the position ofregistry with the markers 4 when the index 12 of the adjusting ring 11registers with the symbol B.

An important advantage of the improved exposure control assembly is thatseveral parts (14, 19, 21, 23, 26) which are needed for automaticdetermination of exposure time and/or aperture size can be used forindication of relatively long exposure times.

Referring to FIG. 2, there is shown a portion of a second still camerawherein all such parts which are identical with or clearly analogous tothe corresponding parts of the first camera are denoted by similarreference characters.

The moving circuit of the exposure control assembly shown in FIG. 2includes a transistor 40 having a collector circuit which includes aresistor 41 and an emitter connected with the base of a secondtransistor 42. The collector circuit of the transistor 42 includes aresistor 43 and the emitter circuit of the transistor 42 includes avariable resistor 44. The collector of the transistor 42 is furtherconnected with a bistable circuit here shown as a flip-flop 45. Theoutput of the bistable circuit 45 is connectable with the coil of themeasuring instrument 2 by way of contacts 20, b of the two-way switch21. The coil of the measuring instrument 2 can be connected with thenegative pole of the energy source 17 by way of the switches 16 and 23.The high-resistance input of the moving circuit including the parts 40,42, 45 is connected with the timer 14, when the index 12 of theadjusting ring 11 registers with the symbol B on the scale 13.

The operation of the camera of FIG. 2 is analogous to that of the firstcamera. A difference between the two cameras is that the switchingcircuit 45 abruptly changes its condition after elapse of an intervalwhich is determined by scene brightness (as measured by thephotosensitive resistor 14) whereby the circuit 45 causes the pointer 3to suddenly move to the position of registry with the markers 4. Whenthe index 12 of the adjusting ring 11 registers with the symbol B of thescale 13, the operator terminates the finger pressure upon the releaseelement 8 to close the shutter as soon as the pointer 3 registers withthe markers 4.

The moving circuit including the transistors 24, 29, 31 of FIG. 1 or thetransistors 40, 42 and the bistable circuit 45 of FIG. 2 can be replacedwith other suitable circuits, for example, with a moving circuitincluding an electronic switching device .(such as a unijunctiontransistor). A moving circuit which employs a unijunction transistorshares the advantages of the circuit shown in FIG. 2, i.e., the pointer3 is caused to suddenly assume the position of registry with the markers4 when the capacitor 25 is charged to a predetermined value.

The auxiliary switch 26 insures that the capacitor 25 is charged onlywhen the index 12 of the adjusting ring 11 registers with the symbol Bof the scale 13.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featureswhich fairly constitute essential characteristics of the generic andspecific aspects of our contribution to the art and, therefore, suchadaptations should and are intended to be comprehended within themeaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:

I. In a photographic apparatus, an exposure control assembly comprisingan electrical moving-coil measuring instrument having an indicatormovable to and from a predetermined position which represents an optimumlength of a relatively long exposure time at a low scene brightness;timer means including photosensitive receiver means exposed to scenelight and capacitor means chargeable by way of said receiver means at arate which is a function of scene brightness; a moving circuit having ahigh-resistance input connectable with said timer means and an outputconnectable with said instrument to effect a movement of said indicatorto said predetermined position in response to charging of said capacitormeans to a predetermined value; switch means actuatable to connect saidoutput with said instrument and to connect said input with said timermeans; and adjusting means for actuating said switch means at the willof the user.

2. An exposure control assembly as defined in claim I, wherein saidmoving circuit comprises a plurality of transistors which are connectedin cascade.

3. An exposure control assembly as defined in claim I, wherein saidmoving circuit comprises a bistable circuit.

4. An exposure control assembly as defined in claim I, wherein saidmoving circuit comprises an electronic switching device.

5. An exposure control assembly as defined in claim 4, wherein saiddevice is a unijunction transistor.

6. An exposure control assembly as defined in claim 1, wherein saidadjusting means is movable between a first position in which said switchmeans connects said receiver means in circuit with said instrument and asecond position in which said switch means connects said receiver meanswith said input and in series with said capacitor means whilesimultaneously connecting said output with said instrument.

7. An exposure control assembly as defined in claim 6, wherein saidswitch means comprises two two-way switches each having a first and asecond position, said switches assuming said first positions in responseto movement of said adjusting means to the first position thereof tothereby connect said receiver means with said instrument, said switchesbeing connected in series in said first positions thereof and beingmoved to said second positions in response to movement of said adjustingmeans to its second position whereby one of said switches connects saidreceiver means with said capacitor means and the other of said switchesconnects said output with said instrument.

8. An exposure control assembly as defined in claim 7, furthercomprising a source of electrical energy, said switch means furthercomprising a third two-way switch movable to a first position inresponse to movement of said adjusting means to the first positionthereof to thereby connect said instrument with one pole of said sourceand to a second position in response to movement of said adjusting meansto the second position thereof to thereby connect said instrument withthe other pole of said source.

9. An-exposure control assembly as defined in claim 6, wherein saidswitch means comprises an auxiliary switch connected in parallel withsaid capacitor means, said auxiliary switch being respectively closedand open in the first and second positions of said adjusting means.

10. An exposure control assembly as defined in claim 1, wherein saidadjusting means comprises a manually operated adjusting member.

11. An exposure control assembly as defined in claim 1, furthercomprising adjustable diaphragm means and adjustable light-obstructingmeans for changing the exposure of said receiver means to scene light independencyon the adjustment of said diaphragm means.

12. An exposure control assembly as defined in claim I, wherein saidindicator is a pointer which is observable from without the photographicapparatus, at least in said predetermined position thereof.

13. An exposure control assembly as defined in claim 1, furthercomprising viewfinder means, said indicator being observable in saidviewfinder means at least in said predetermined position thereof.

14. An exposure control assembly as defined in claim 1, furthercomprising marker means for pinpointing said predetermined position ofsaid indicator.

[5. An exposure control assembly as defined in claim 1,

from a starting position into engagement with said indicator andblocking means controlled by said adjusting means and arranged to blockthe movement of said scanning means into engagement with said indicatorwhen said adjusting means actuwherein said indicator is movable to aplurality of additional ates Said Switch meanspositions and furthercomprising scanning means movable

1. In a photographic apparatus, an exposure control assembly comprisingan electrical moving-coil measuring instrument having an indicatormovable to and from a predetermined position which represents an optimumlength of a relatively long exposure time at a low scene brightness;timer means including photosensitive receiver means exposed to scenelight and capacitor means chargeable by way of said receiver means at arate which is a function of scene brightness; a moving circuit having ahighresistance input connectable with said timer means and an outputconnectable with said instrument to effect a movement of said indicatorto said predetermined position in response to charging of said capacitormeans to a predetermined value; switch means actuatable to connect saidoutput with said instrument and to connect said input with said timermeans; and adjusting means for actuating said switch means at the willof the user.
 2. An exposure control assembly as defined in claim 1,wherein said moving circuit comprises a plurality of transistors whichare connected in cascade.
 3. An exposure control assembly as defined inclaim 1, wherein said moving circuit comprises a bistable circuit.
 4. Anexposure control assembly as defined in claim 1, wherein said movingcircuit comprises an electronic switching device.
 5. An exposure controlassembly as defined in claim 4, wherein said device is a unijunctiontransistor.
 6. An exposure control assembly as defined in claim 1,wherein said adjusting means is movable between a first position inwhich said switch means connects said receiver means in circuit withsaid instrument and a second position in which said switch meansconnects said receiver means with said input and in series with saidcapacitor means while simultaneously connecting said output with saidinstrument.
 7. An exposure control assembly as defined in claim 6,wherein said switch means comprises two two-way switches each having afirst and a second position, said switches assuming said first positionsin response to movement of said adjusting means to the first positionthereof to thereby connect said receiver means with said instrument,said switches being connected in series in said first positions thereofand being moved to said second positions in response to movement of saidadjusting means to its second position whereby one of said switchesconnects said receiver means with said capacitor means and the other ofsaid switches connects said output with said instrument.
 8. An exposurecontrol assembly as defined in claim 7, further comprising a source ofelectrical energy, said switch means further comprising a third two-wayswitch movable to a first position in response to movement of saidadjusting means to the first position thereof to thereby connect saidinstrument with one pole of said source and to a second position inresponse to movement of said adjusting means to the second positionthereof to thereby connect said instrument with the other pole of saidsource.
 9. An exposure control assembly as defined in claim 6, whereinsaid switch means comprises an auxiliary switch connected in parallelwith said capacitor means, said auxiliary switch being respectivelyclosed and open in the first and second positions of said adjustingmeans.
 10. An exposure control assembly as defined in claim 1, whereinsaid adjusting means comprises a manually operated adjusting member. 11.An exposure control assembly as defined in claim 1, further comprisingadjustable diaphragm means and adjustable light-obstructing means forchanging the exposure of said receiver means to scene light independency on the adjustment of said diaphragm means.
 12. An exposurecontrol assembly as defined in claim 1, wherein said indicator is apointer which is observable from without the photographic apparatus, atleast in said predetermined position thereof.
 13. An exposure controlassembly as defined in claim 1, further comprising viewfinder means,said indicator being observable in said viewfinder means at least insaid predetermined position thereof.
 14. An exposure control assembly asdefined in claim 1, further comprising marker means for pinpointing saidpredetermined position of said indicator.
 15. An exposure controlassembly as defined in claim 1, wherein said indicator is movable to aplurality of additional positions and further comprising scanning meansmovable from a starting position into engagement with said indicator andblocking means controlled by said adjusting means and arranged to blockthe movement of said scanning means into engagement with said indicatorwhen said adjusting means actuates said switch means.